| Sumario: | Rice ratoon cropping, or the cultivation of tillers that have re-grown from existing stem nodes of 8 a harvested crop, is currently a hot topic in agriculture with record-high ratoon crop yields being 9 achieved in China (Xu et al., 2021). Although rice ratoon cropping is most appropriate for certain 10 agro-ecosystems with a suitable climate and cropping schedule, it is a promising strategy to 11 simultaneously increase productivity while reducing inputs and labor. Rice ratoon cropping may 12 thereby contribute to global food security and agro-ecosystem sustainability. However, the 13 advances in increasing ratoon crop productivity to date have been largely based on agronomic 14 strategies such as nutrient management, water management, and mechanization (Wang et al. 15 2020). Some existing varieties have been identified to have good ratooning ability (although this 16 often depends on multiple factors such as soil moisture and stubble cutting height). Some QTLs 17 related to ratooning have been identified (eg Hu et al., 2022), but very little breeding work 18 (crossing and selecting) has been conducted for ratooning ability and currently no rice variety 19 has been released specifically for its ratooning ability. Recently, perenniality-related traits have 20 been introgressed into Oryza sativa from Oryza longistaminata (Zhang et al., 2023); this 21 material may be useful for annual ratoon rice but is generally targeting a different agronomic 22 system. Newly-developed rice varieties with known ratooning ability are needed to help increase 23 rice productivity sustainably.
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